Determinants of number-specific recall error of last menstrual period: a retrospective cohort study

Abstract Purpose The aim of this study was to examine the association between periconceptional folic acid (FA) supplementation and risk of preterm birth. Methods We conducted a retrospective cohort study in women aged 18–49 who participated in the NFPHEP from 2010 to 2018, and had a singleton livebirth in 129 counties in southwest China. Participants were divided into four groups according to the time period starting FA use: no use, after the last menstrual period, at least 1–2 months before the last menstrual period, at least 3 months before the last menstrual period. The outcomes were preterm birth (gestation < 37 weeks) and early preterm birth (gestation < 34 weeks). Results 201,477 women were included and 191,809 (95.2%) had taken FA during periconception. Compared with women who did not take FA, women who started taking FA 1–2 months before their last menstrual period had a 15% lower risk of preterm birth (aOR = 0.85, 95% CI 0.79–0.92), and women who started taking FA at least 3 months before their last menstrual period had a 20% lower risk of preterm birth (aOR = 0.80, 95% CI 0.75–0.87), but women who started taking FA after their last menstrual period did not appear to reduce the risk of preterm birth. Conclusions In this study of 200,000 Chinese women, periconceptional supplementation with FA was associated with a lower risk of preterm birth. Women who started taking FA at least 3 months before their last menstrual period were more likely to reduce the risk of preterm birth.

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Effect of COVID-19 vaccination on menstrual periods: a retrospective cohort study

10.22541/au.163943767.74401646/v1 ◽

2021 ◽

Author(s):

Victoria Male

Keyword(s):

Cohort Study ◽

Menstrual Cycle ◽

Outcome Measures ◽

Retrospective Cohort Study ◽

Retrospective Cohort ◽

Hormonal Contraception ◽

Menstrual Period ◽

Study Setting

Objective. Clinicians and regulators are receiving reports of changes to menstrual periods following COVID-19 vaccination. However, it is unclear if the two are biologically linked. If they are, people using hormonal contraception are predicted to be less likely to report a change and spontaneously cycling people vaccinated prior to ovulation more likely. The objective was to test these hypotheses. Design. Retrospective cohort study. Setting. UK. Population. 1273 people who had received at least one dose of a COVID-19 vaccination, have periods or withdrawal bleeds and keep a record of the dates of these. Methods. Participants reported whether they use any hormonal contraception and, for each dose of the vaccine, on which day of their menstrual cycle they were vaccinated and details of how the timing and flow of their next period compared to their normal experience. Main outcome measures. Association between 1. the use of hormonal contraception and reported changes to timing or flow of the next menstrual period, and 2. the timing of vaccination within the menstrual cycle and reported changes to timing or flow of the next menstrual period. Results. The data from this cohort did not support the pre-specified hypotheses that people using hormonal contraception would be less likely to report a change, or that spontaneously cycling people vaccinated prior to ovulation would be more likely to report a change. Conclusions. This study did not detect strong signals supporting the idea that COVID-19 vaccination is linked to menstrual changes in most people. Funding. No specific funding.

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